This invention relates generally to wavelength division multiplexing.
Wavelength division multiplexing (WDM) is an optical communication technique that leverages the enormous bandwidth of an optical fiber. A WDM system may include a plurality of laser light sources, conventionally implemented by laser diodes that produce a plurality of wavelength separated data streams. The independent data streams are then multiplexed together on a single output fiber. Allowing multiple WDM channels to coexist on a single fiber, one can tap into the huge available fiber bandwidth with data rates exceeding several tens of gigabits per second.
A multi-wavelength light source emits light at precisely determined wavelengths with a precisely determined inter-wavelength spacing. Discrete laser sources and small arrays of sources are commercially available. Laser outputs of different wavelengths may be made available from a single chip. The light beams of multiple wavelengths may ultimately be combined for transmission over a single-mode fiber. Such an approach provides an integrated solution that reduces packaging cost while improving performance.
An integrated laser array may be formed of a multiple wavelength InGaAsP/InP strained multi-quantum well (MQW) gain-coupled distributed-feedback (DFB) laser array including several ridge waveguide lasers with ridge widths from 1.5 to 5 micrometers. See xe2x80x9cMulti-Ridge Waveguide Gain-Coupled DFB Laser Array,xe2x80x9d by G. P. Li et al., JLT, Vol. 13, No. 2 pp. 196-199 (1995).
Even with an integrated laser array, a separate multiplexer is utilized to couple the different light beam wavelengths into a single mode fiber. This increases the packaging costs and necessarily results in insertion losses. Given sufficient numbers of multiplexers and de-multiplexers, significant power losses may result in large optical networks.
Thus, there is a need for better ways to couple integrated laser light sources to multi-mode fibers.